(1) Field of the Invention
The present invention relates to novel cephalosporin derivatives valuable as medicines and processes for the preparation thereof.
More particularly, the present invention relates to novel cephalosporin derivatives having an excellent antibiotic activity against pathogenic bacteria belonging to the general Pseudomonas, Serratia and Enterobacter, and processes for the preparation thereof.
(2) Description of the Prior Art
Japanese Patent Application Laid-Open Specification No. 148795/79 (Richardson-Merrell Incorporated) discloses that a compound represented by the following formula has an excellent antibiotic property: ##STR4##
wherein A is selected from the group consisting of sigma bond, phenylene and phenylenethio, R.sub.1 is selected from the group consisting of hydrogen, phenyl, amino, hydroxyl, carboxyl and sulfo, R.sub.2 is selected from the group consisting of hydrogen, formyloxymethyl and alkanoyloxymethyl (in which the alkanoyl group has 2 to 5 carbon atoms), and R.sub.3 is selected from the group consisting of hydrogen, hydroxyl, acetoxy, 5-methyl-1,3,4-thiadiazol-2-yl-thio, 1-methyl-1,2,3,4-tetrazol-5-yl-thio and 1,2,3-triazol-4-yl-thio.
It is suggested by the above laid-open specification that when a 1,3-dithiolan-2-imino group is introduced into a known cephalosporin compound, the antibiotic activity against gram-negative bacteria and gram-positive bacteria is enhanced.
The compound disclosed in the above laid-open specification is very low in effect in the curing of infectious diseases caused by, Pseudomonas, Serratia and Enterobacter, which are now regarded as being difficult to cure.
A series of cephalosporin compounds are disclosed in Japanese Patent Application Laid-Open Specifications Nos. 82286/76, 110592/76, 15398/78, 79895/78 and 39091/79 (all filed by Bayer A.G.), but cephalosporin compounds having a 1,3-dithiolan-2-imino group are not disclosed in any of these laid-open specifications.